Proximity sensor devices (also commonly called touchpads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, which uses capacitive, resistive, inductive, optical, acoustic and/or other technology to determine the presence, location and/or motion of one or more fingers, styli, and/or other objects. The proximity sensor device, together with finger(s) and/or other object(s), may be used to provide an input to the electronic system. For example, proximity sensor devices are used as input devices for larger computing systems, such as those found integral within notebook computers or peripheral to desktop computers. Proximity sensor devices are also used in smaller systems, including handheld systems such as personal digital assistants (PDAs), remote controls, digital cameras, video cameras, communication systems such as wireless telephones and text messaging systems. Increasingly, proximity sensor devices are used in media systems, such as CD, DVD, MP3, video or other media recorders or players.
Many electronic devices include a user interface (UI) and an input device for interacting with the UI (e.g., interface navigation). A typical UI includes a screen for displaying graphical and/or textual elements. The increasing use of this type of UI has led to a rising demand for proximity sensor devices as pointing devices. In these applications the proximity sensor device may function as a value adjustment device, cursor control device, selection device, scrolling device, graphics/character/handwriting input device, menu navigation device, gaming input device, button input device, keyboard and/or other input device. One common application for a proximity sensor device is as a touch screen. In a touch screen, the proximity sensor is combined with a display screen for displaying graphical and/or textual elements. Together, the proximity sensor and display screen function as the user interface.
In recent years, proximity sensor devices, such as touch screens, have been developed which include systems for determining the force applied by the input object onto input device in the sensing region, in addition to the positional information associated with the input object. Systems have tried to generate indirect estimates of force input using the readings that are also used to determine the positional information. However, such methods are generally unreliable and inaccurate. Other current force determining systems utilize technologies that are completely independent of those that are used to determine the positional information, which often results in increases in the costs of the devices.
There is a continuing need for improvements in input devices. In particular, there is a continuing need for improvements in force sensing systems.